In modern brain surgery, surgeons often use optical microscopes and/or specialized imaging devices to view the brain. There has, however, been a long felt need for a highly accurate and timely manner of displaying local brain functions to a surgeon. At present, methods which are accurate require significant amounts of time at the beginning of an operation, which pose an increased risk to the patient. Conversely, methods which require less time during the operation to configure are less accurate and pose corresponding risks.
When operating in a brain, it is vital for a surgeon to know which portions of the brain in the operation site are eloquent areas, the removal of which will result in loss of motor function, sensory function, language function, vision etc. Currently, a common method for determining these local brain functions is to physically stimulate a plurality of locations of an exposed brain, normally in the form of a grid, with a probe delivering a short pulse of electric current, and then determining if there is a corresponding visual or measureable response from the patient. When a response is elicited, then that point in the brain is tagged as a functional point. If no response is elicited, then that point is deemed safe to cut through.
More recently, prior to an operation, a patient may undergo NBS for functional mapping. The extent of the mapping can be determined based on the particulars of the impending operation. For example, in the case where a tumor is to be removed from a patient's brain, the NBS functional mapping can be restricted to mapping the functions of the brain within the immediate vicinity of the tumor. In the case of an exploratory or more invasive surgery, the functional mapping can be more extensive.
NBS functional mapping is a non-invasive method of accurately mapping a patient's brain functions through the use of navigated Transcranial Magnetic Stimulation (TMS). By applying an electro-magnetic stimulation to a location on, or within, a patient's brain, and measuring and/or determining a patient's corresponding response, it is possible to provide an accurate 2- or 3-dimensional map of the patient's brain in a non-sterile environment. More detailed descriptions of 2-dimensional and 3-dimensional NBS functional mapping can be found, for example, in US 2008/058582, “Transcranial magnetic stimulation induction coil device with attachment portion for receiving tracking device”, US 2005/075560, “Stereotactic frame and method for supporting a stereotactic frame”, U.S. Pat. No. 7,720,519, “Method for three-dimensional modeling of the skull and internal structures thereof”, U.S. Pat. No. 11/853,232, “A method for visualizing electric fields on the human cortex for the purpose of navigated brain stimulation”, U.S. Pat. No. 11/853,256, “Improved accuracy of navigated brain stimulation by online or offline corrections to co-registration”, US 2008/058582, “Transcranial magnetic stimulation induction coil device with attachment portion for receiving tracking device”, US 2008/058581, “Transcranial magnetic stimulation induction coil device and method of manufacture”, U.S. Pat. No. 6,849,040, “Method and apparatus for dose computation of magnetic stimulation”, U.S. Pat. No. 7,440,789, “Electrode structure for measuring electrical responses from the human body”, all of which are herein incorporated by reference.
As is described in more detail in at least some of the above mentioned references, at the beginning of, or prior to, NBS functional mapping, a model of the patient's brain is obtained or selected for mapping. Although a number of options are available, as described therein, according to an embodiment of the present invention, an MRI or a CT of the patient's brain is utilized as the anatomical model for mapping. Once the MRI data has been compiled, then through knowing the exact location and orientation of the patient's head and each TMS pulse, it is possible to accurately map the functions of the patient's brain to the anatomical model.